Monmouth County is a county located in CentralNew Jersey, in the United States within the New York metropolitan area and located in the central part of the state. It is the northernmost county along the Jersey Shore. Monmouth County had a Census-estimated population of 628,715 in 2015, representing a decrease of 0.3% from the 2010 Census, when the population was enumerated at 630,380, in turn an increase of 15,079 from 615,301 at the 2000 Census, falling to the fifth-most populous county in the state, having been surpassed by Hudson County in 2010. As of the 2014 Census Estimate, the county’s population was 629,279. Its county seat is Freehold Borough.The most populous place was Middletown Township, with 66,522 residents at the time of the 2010 Census, while Howell Township covered 61.21 square miles, the largest total area of any municipality.

Monmouth County ranked 38th among the highest-income counties in the United States as of 2011, placing it among the top 1.2% of counties by wealth. As of 2009, it was ranked 56th in the United States by personal per-capita income.

Monmouth County was established on March 7, 1683, while part of the province of East Jersey. On October 31, 1693, the county was partitioned into the townships of Freehold, Middletown and Shrewsbury.